Time-Resolved Spectroscopy of Scintillation Materials using X-RAY Synchrotron Radiation
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117234, Russia
"**Institutefor Nuclear Physics,
Novosibirsk, Russia
ABSTRACT The time-resolved luminescence spectra and decay kinetics of BaF 2 , BGO, and CeF 3 , ..... fizrcnt of were measured with the dissector technique using X-ray synchrotron radiation k,,S'R) spectral composition from wiggler mounted at VEPP-3 storage ring (Novosibirsk). Two effects of X-ray excitation energy on the luminescence parameters were observed: modifications of the emission spectrum and acceleration of decay kinetics. Under the excitation by soil X-ray SR the 220 nm emission band for BaF 2 is broadened, whereas shorter wavelength part of CeF 3 and BGO emission spectra increases. For luminescence decay of excitons and crossluminescence the degree of the deviation from the single exponential law depends on the photon energies and increases under soft X-ray excitation as well. These effects are supposed to be due to the interaction of electronic excitations created after the relaxation of deep core holes. Fast intrinsic luminescence was observed for Cdl2, and CsPbCI 3 under X-ray SR excitation. 500 nm band of Cdl 2 has characteristic time r=4.6 ns, whereas 420 nm band of CsPbCl 3 shows very fast decay with T=0.2 ns.
INTRODUCTION The investigations of luminescence excitation of ionic crystals in the VUV (6-120 eV) have demonstrated that in the process of relaxation of a core hole or of a hot electron, local regions with high density of electronic excitations (HDLR) are created. There are two or more interacting electronic excitations in such regions with the distance between them of the order of' radius of dipole-dipole interaction (1-10 nm). Interaction of these adjacent excitations can lead to the distortion of the luminescence spectra [1], to the creation of new emission centers [2], and to luminescence quenching [3,4]. In the latter case the acceleration of the initial stage of decay kinetics reflects the quenching effect. The spatial distribution of secondary electronic excitations (EEs) after y- or X-ray excitation in ionic crystals and the effects due to the creation of HDLR are scarcely studied. The aim of the present investigation is the study of the dependence of luminescent characteristics of a series of efficient scintillators on the spectral composition of the incident X-rays. Such investigations are useful to understand the mechanism of the relaxation of the primary electronic excitations created by high energy photons, and to predict the scintillation properties of crystals. 235 Mat. Res. Soc. Symp. Proc. Vol. 348. 01994 Materials Research Society
EXPERIMENTAL ARRANGEMENT
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Fig. 1. The spectra of SR incident on the sample In fig. 1 the spectrum of the 'white' X-rays from wiggler of VEPP-3 storage ring, incident on the sample is presented. The long wavelength cut-off of the spectrum (about I KeV) is due to the absorption of the Be foil in the beamline. The duration of the SR pulses
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